On the safety /legality issue, here in the UK there have been various moves to try to ban poppers. In fact it comes up every so often, most recently with the banning of so-called 'legal highs', those synthetic carabinoids etc that are made in labs. Some politicians wanted to include poppers in that category but the evidence against them was examined again and, again, it was concluded they didn't pose a significant enough risk to ban them.
Here their sale is controlled in the sense that you can really only get them in sex shops, although I've noticed recently that some of the milder brands are now on sale in general stores, tobacconists, even souvenir shops(!) in central London - which surprises me. That seems to suggest that regulation is actually loosening around them.
And if course there are many online retailers now. They offer best value for money. I was in and around Soho in central London last night, and the sex shops there were offering supermarket-style bulk-buy deals on poppers. £9 for 1 bottle of the newer, stronger brands, or 4 for £25. This is the way it is going. Online I can get 2 for maybe £12, but you have to add shipping to that.